Production wells that are not being used are properly plugged to avoid any oil and gas reservoir fluids from migrating uphole and possibly contaminating other formations or fresh mud aquifers. The process of plugging and abandoning of oil and gas wells requires new technologies to confirm that there is no fluid path in the second cement annulus between the outer casing and formation. Even though existing ultrasonic measurements (50 to 500 kHz) provide a reliable way to diagnose imperfect cement in the first annulus, there are no commercially available measurements that would reliably detect the presence of imperfect cement in the second annulus that might impair hydraulic isolation between the hydrocarbon bearing and adjacent layers of earth.